Hidden hinges of many types and shapes are widely applied to hinge doors (both wooden and glass) of cupboards. As shown in FIG. 1, the structure of the many hinges is but a base saddled) with a hollow opening(11) that contains a group of plates(2) with folding actions by which a link(3) connected to the plates(2) and a base saddle(4) can be foldedly-turned within a 90.degree.. The application of the structure is to fix the base saddled) on the door plate and attach the base saddle(4) to the cupboard, so that the action of the plates(2) and link(3) can open and shut the door within a right angle. Yet, in order to shut the door firmly, a contraction spring(5) is usually equipped on the joint of plates(2) and link(3) of most hinges. Despite that the contraction of the spring(5) shall hold the door tight against the cupboard or shut it automatically, the installation of the spring is that inconvenient and time consuming, and as the contraction is strong, it sometimes pushes the door to the cupboard which that makes so loud a noise and even damages the door or the glass door, the losses both countable and uncountable of hidden hinges would somewhat degrade their value of application.